Technology: Moon rocks may help colonisers breathe easy

Future colonists of the Moon will not have to take oxygen with them
from Earth. Instead, they will be able to extract it from Moon rocks using
a chemical process recently tested in simulated lunar conditions in the
US.

Chris Knudsen, a co-developer of the process and the founder of Carbotek
Development Laboratories in Houston, says his technique liberates the oxygen
which exists in ilmenite, a mineral abundant in lunar soil. The system will
save colonisers the enormous energy and expense of bringing oxygen with
them to the Moon. They will still need to bring hydrogen which is essential
for the process, but hydrogen is only one-eighth the mass of oxygen.

Carbotek recently mounted tests of its process aboard a NASA research
aircraft. By following a precise parabolic path, the plane can simulate
the reduced amount of gravity on the Moon. ‘We ran three flights at lunar
gravity on terrestrial ilmenite minerals typical of those in the lunar soil,’
says Knudsen. In addition, the company is working with mathematical models
of the reactor design, taking into account the behaviour of lunar soil and
fluid flow in lunar conditions.

The process requires temperatures of around 1000 °C and pressures
of between 7 and 14 atmospheres. It involves blowing hydrogen through fine
ilmenite particles less than 300 micrometres across to produce a fast-moving
mixture known as a fluidised bed.

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Knudsen explains that the fluidised bed has three layers: the ilmenite,
an oxide of iron and titanium (FeTiO3), is fed into the top of
the reactor and meets hydrogen pumped up through the bottom layer. ‘The
top and bottom layers maintain the heat transfer and the central one is
the reactor bed,’ he says.

The hydrogen reacts with the oxide in the rock to form water, and the
gaseous mixture of water vapour and hydrogen passes to an electrolysis unit
where the hydrogen and oxygen in the water are separated. ‘Essentially,
you are putting in soil and energy and taking out spent soil and oxygen,’
Knudsen says.

The oxygen is liquefied and stored and the hydrogen recycled to the
reactor. However, he says, the process is energy intensive, and the energy
input would come either from solar panels on the Moon or from nuclear reactors.
Because lunar days and nights each last two Earth weeks, solar energy generated
in the lunar day would have to be stored for use at night.

The energy would also be needed to concentrate the ilmenite. The mineral
is weakly magnetic and could be separated from unwanted silicon-based basaltic
rock with electric or magnetic fields.

Carbotek is working with the company Shimizu of Tokyo to adapt their
system into a process for hydrating cement that colonisers could use for
building. Shimizu has devised a process for mixing concrete in a vacuum,
similar to conditions on the Moon. The cement would consist of materials
available on the lunar surface, but would require water for mixing.

Knudsen says that the Carbotek system is under evaluation by NASA, and
his company is working towards a pilot development stage. He says the next
mission to the Moon may be as soon as 2002, and the first lunar oxygen extraction
plant could be in place by around 2007.